RCgothic

If you drill small holes in the corners of a square feature it takes much of the stress out and you wouldn't spot them at this resolution. Got to assume they know what they're doing.

Don't really know where else to put this, but it's brilliant!

Elon has said it will be stable unpressurized.

This is of course the important bit! :-D

I had a bad feeling when the link cut out. It wasn't low enough for LOS. Then there was the callout "1st stage LOS expected" and I didn't expect it to make it.

Rockets are constant thrust devices. It doesn't how fast you're going, they push the same regardless. Work is force times distance. If you apply 10N to a stationary block and it doesn't move, you've done no work. If you apply 10N to a trolley going 1m/s, you've done 10J of work. If you apply 10N to a rocket going 10,000m/s, you've done 100kJ of work. Rockets are therefore more efficient when they're going fast. The fastest part of an orbit is deep in a gravity well. Only velocity parallel to the direction of motion counts, so burning sideways is equivalent to a standing start.

A huge expendable Saturn V style booster would have been fine; if it were much, much cheaper, probably as a result of not being man-rated. There's no reason for crew to go up on a big booster and make both functions more expensive by association.

That wasn't that useful a function.

I said probably because there's always a chance something could go wrong with Demo2.

SLS in current version (Block 1) is too underpowered (and Orion too overweight) to recreate Apollo. Block 1B can't do so either, and its future looks shaky. Block 2 could, but it's so far over the horizon as to be effectively never. SLS is effectively what you'd get it they hadn't decided to all-up test Apollo/SaturnV and the lightened Apollo Block 2 had been cancelled along with SII. Not enough rocket, too much capsule. Also I note that Falcon 9 will probably be man-rated before SLS will.

This exactly. Block 1B can't do Orion and a useful payload, so it's dead. Block 2 could, but it's so far over the horizon as to be effectively never. So we're stuck with Block1. Block 1 requires commercial support. Many launches of commercial support, with rendezvous somewhere around the moon. And if you're requiring commercial support then commercial rockets are more than capable of both putting the CSM in orbit *and* delivering separately a naked second stage with residuals to dock to and serve as an earth departure stage, and of doing it again for a lander. It's more moving parts, sure. More moving parts than rendezvousing at a gateway in LLO? Nope. So what exactly is the point of Block1? How many flights does it take to man-rate Falcon Heavy? 7? Guaranteed to cost less than EM1.

Of course the danger to SLS is that if you can decide "Orion and not-a-lander to TLI" is not meaningfully better than "Orion Only to TLI", then what's to stop "Not-Orion on not-SLS to TLI". There are a number of commercial options nearing completion. And nothing of value would be lost./s

So block 2 is over the horizon, and block 1B is now on the chopping block as well. I guess the difference between "can send Orion Only to TLI" and "can send Orion and not-a-lander to TLI" just isn't big enough.

Because for spacex it was cheaper and faster to physically demonstrate their cheap and rapidly reusable booster than to perform exhaustive analysis. Both approaches are valid.

Hydrolox is daft as a first stage anyway. Too low-thrust when the rocket is heaviest. Unnecessarily bulky for assembly, transport and pad infrastructure. Unnecessarily high cross-section for when the rocket is transiting the densest atmosphere.